In the related art, there are three types of infrared light shielding laminates. Firstly, an infrared light shielding laminate is disclosed (for example, see Patent Document 1), and the infrared light shielding laminate includes a transparent dielectric layer, an infrared reflective layer, and a transparent dielectric layer in this order, and each transparent dielectric layer mainly consists of zinc oxide and the infrared reflective layer mainly consists of silver. A glass laminate having a heat-ray reflective film (infrared light shielding laminate) which consists of such a laminate and is formed on a glass surface has a film surface with a low emissivity, and therefore, the glass laminate is referred to as low emissivity glass (Low-E glass).
Secondly, an infrared light shielding laminate is disclosed (for example, see Patent Document 2), and the infrared light shielding laminate includes a thin base film consisting of ITO or the like, a thin metal film mainly containing Ag, and a thin protective film consisting of SnO2 or the like in this order on the surface of a glass substrate, and these thin films are formed using a sputtering method. A heat-ray shielding glass which includes a glass substrate and the above-described infrared light shielding laminate formed on the surface of the glass substrate has a thin Ag film with excellent transparency to visible light and excellent reflectance of near infrared light and also has excellent durability.
Thirdly, an infrared light shielding laminate is disclosed (for example, see Patent Document 3), and the infrared light shielding laminate includes: a heat-ray reflective film that is formed on at least one surface of a glass substrate and has a layer containing silver as a main component; and a heat insulation protective film formed on the surface of the heat-ray reflective film. The heat insulation protective film includes a matrix containing silicon oxide as a main component and an infrared absorbent dispersed in the matrix. The infrared absorbent consists of fine particles of an inorganic compound such as ITO, ATO, LaB6, or the like. The fine particles of the inorganic compound are nanoparticles having an average primary particle diameter of 100 nm or less. The infrared light shielding laminate has wear resistance and moisture resistance and exhibits heat shielding properties.
With regard to an ITO particle film in which ITO particles are not in contact with each other but adjacent to each other, a phenomenon occurring when light in a near infrared region and an infrared region is incident on the ITO particle film (the light enters the ITO particle film) has been published (for example, Non-Patent Document 1). The electric field of surface plasmons excited by the light is strengthened due to near field effects occurring within the distance between particles. The plasmon resonance light is radiated so that reflection occurs. From this publication, approaches are presented for new research and development of a blocking technique of heat rays having high reflection performance by controlling the spatial arrangement of nanoparticles and the light phenomenon of the near field.
However, the infrared light shielding laminate disclosed in Patent Document 1 is colored and has a low light transmittance. Therefore, there is a problem in that the infrared light shielding laminate is not suitable for applications for products with a limited transmittance such as windshields of automobiles.
The infrared light shielding laminate disclosed in Patent Document 2 reflects near infrared light. Accordingly, the infrared light shielding laminate has more excellent thermal insulation characteristics than the infrared light shielding laminate disclosed in Patent Document 3. However, since the infrared light shielding laminate of Patent Document 2 is a continuous film having a low resistance, radio waves are also shielded. For this reason, radio waves of an electronic toll collection system (ETC) and mobile phones are absorbed and reflected and this may cause communication failure. This problem can be overcome by patterning the infrared light shielding laminate through etching, but the production process is complicated and thus the cost is high.
The infrared light shielding laminate disclosed in Patent Document 3 is more excellent than the infrared light shielding laminates of Patent Documents 1 and 2 from the viewpoints of the transmittance of visible light, radio wave transparency, and simplicity of the production process. However, since nanoparticles absorb infrared light, the total thermal insulation characteristics of the infrared light shielding laminate of Patent Document 3 are not superior to those of the infrared light shielding laminates of Patent Documents 1 and 2, and there are problems to be further improved.
In the ITO particle film disclosed in Non-Patent Document 1, spatially arranged nanoparticles are easily peeled off from the film. Therefore, problems still remain in practical use of the film.